Detection of intense plankton blooms using the 709 nm band of the MERIS imaging spectrometer

Intense plankton blooms ( colloquially called 'red tides') are becoming an increasingly important phenomenon in coastal waters. This Letter shows how the European satellite sensor MERIS ( Medium Resolution Imaging Spectrometer) can be used to detect a peak in the optical spectrum of water-leaving radiance near 705nm which provides a more specific response to some types of these blooms. Images and spectra are presented, derived from a MERIS scene where small areas have this response. One such area is at the site of a fish farm where bloom conditions were confirmed by surface observations and measurements. The observed spectra are compared to model results to demonstrate how these responses arise. Inspection of data from other parts of the world shows similar features in US and European waters.